1. Field of the Invention
The present invention relates to a class of lubricant additives. More particularly, the present invention relates to a class of lubricant additives that is derived from the condensation of an alkylated diphenylamine (ADPA) with a ketone or aldehyde in the presence if a suitable acidic catalyst.
2. Description of Related Art
The reaction products of a diarylamine and an aliphatic ketone are known antioxidants. Among the known diarylamine aliphatic ketone reaction products are those that are disclosed in U.S. Pat. Nos. 1,906,935; 1,975,167; 2,002,642; and 2,562,802. Briefly described, these products are obtained by reacting a diarylamine, preferably a diphenylamine, which may, if desired, possess one or more substituents on either aryl group, with an aliphatic ketone, preferably acetone, in the presence of a suitable catalyst. In addition to diphenylamine, other diarylamine reactants known in the art include dinaphthyl amines; p-nitrodiphenylamine; 2,4-dinitrodiphenylamine; p-aminodiphenylamine; p-hydroxydiphenylamine; and the like. In addition to acetone, other ketone reactants known in the art include methylethylketone, diethylketone, monochloroacetone, dichloroacetone, and the like.
A commercially available diarylamine-aliphatic ketone reaction product is one that is obtained from the condensation reaction of diphenylamine and acetone (NAUGARD A, Uniroyal Chemical) that can be prepared in accordance with the conditions described in U.S. Pat. No. 2,562,802. The commercial product is supplied as a light tan-green powder or as greenish brown flakes and has a melting range of 85° to 95° C.
A variety of factors contribute to, or have an essential bearing on, the nature of the final reaction product of ketones and secondary amines. Among such factors are the type and concentration of catalyst, the concentration and nature of the primary reactants, and the temperature level used throughout the reaction.
Several ways have long been known in the art for condensing diphenylamine and acetone to give antioxidant products ranging from solid materials (U.S. Pat. No. 2,002,642) to heavy liquids, see U.S. Pat. No. 1,975,167, which discloses an autoclavic preparation of the condensate of acetone and diphenylamine.
U.S. Pat. No. 2,202,934 discloses a process comprising passing an aliphatic ketone in vapor form into a liquified diarylamine and reacting the two materials in the presence of a catalyst and under conditions whereby a high degree of conversion of the diarylamine is obtained. The preferred catalysts are those containing halogen, e.g., iodine, bromine, hydriodic acid, hydrobromic acid, and hydrochloric acid. The temperatures employed are in the range between 100° C. and about 200° C.
U.S. Pat. No. 2,562,802 discloses a process wherein acetone and diphenylamine are autoclaved at a temperature of 275-310° C. and at a pressure greater than atmospheric, for from 3 to 10 hours, preferably in the presence of at least one catalyst such as iodine, hydriodic acid, bromine, hydrobromic acid, or the bromides and iodides of the non-lead heavy metals, especially ferrous iodide.
U.S. Pat. No. 2,650,252 discloses that the condensation of aliphatic ketones and diarylamines can be promoted by a halogenated hydrocarbon selected from the class consisting of haloalkanes, haloalkenes, halocycloalkanes, and haloalkyl benzenes, having in each case a halogen atom directly linked to a saturated carbon atom, and further the halogen in each case having an atomic weight of at least 35.
U.S. Pat. No. 2,657,236 discloses that the condensation of aliphatic ketones and diarylamines can be promoted by a catalyst selected from the class consisting of halogenated organic acids, esters of halogen-containing organic acids and amides of halogenated organic acids, in which a halogen substituent is directly linked to a saturated acyclic carbon atom.
U.S. Pat. No. 2,660,605 discloses the conversion of a relatively hard resinous aliphatic ketone-diarylamine antioxidant to a mobile oily material having a viscosity of from about 10 to about 50 poises, measured at 30° C., by heating with an alkylated benzene in which at least one alkyl group is at least two carbons in length and has at least one hydrogen on the carbon atoms alpha and beta to the benzene ring, i.e., primary and secondary alkyls.
U.S. Pat. No. 2,663,734 discloses that the condensation of aliphatic ketones and diarylamines can be promoted by a halogenated aldehyde or acetal (open chain or cyclic), the halogen having an atomic weight of at least approximately 35.
U.S. Pat. No. 2,666,792 discloses that the condensation of aliphatic ketones and diarylamines can be promoted by an acyl halide.
U.S. Pat. No. 5,268,394 discloses acridans of the structure
wherein R1, R2, R3, and R4 can be H, C1-C18 alkyl, or C7-C18 aralkyl. R3 and R4 can also be aryl, preferably phenyl. The compound can be used as a stabilizer, preferably combined with hindered amine, phenolic, and phosphite stabilizers for stabilizing polyether polyols for polyurethane flexible foams and as stabilizers for the polyglycols, heat transfer fluids, and lubricating additives.
Tritschler, W. et al., Chem. Ber. 117:2703-2713 (1984) reported spiroacridans of a particular formula could be easily obtained by condensation of certain diarylamines and cyclic ketones.
The disclosures of the foregoing are incorporated herein by reference in their entirety.